Methods and apparatus for carrying out backoff operations

ABSTRACT

A method is carried out on a device capable of utilizing a high efficiency wireless local area network (HEW) communication protocol and a legacy communication protocol, and includes wirelessly receiving a communication frame; when the measured energy level of the frame exceeds a static clear channel assessment (CCA) energy level, identifying the BSS to which the frame corresponds, wherein identifying the BSS to which the frame corresponds comprises utilizing a BSS identifier included in the frame when the frame is an HEW frame or utilizing a MAC address included in the frame when the frame is a legacy frame; when the frame corresponds to the same BSS as the device, processing the frame utilizing the static CCA energy level; and when the frame corresponds to an overlapping OBSS, processing the frame utilizing a dynamic CCA energy level.

CROSS-REFERENCE TO RELATED APPLICATION

This disclosure claims the benefit of U.S. Provisional PatentApplication No. 62/088,245, filed Dec. 5, 2014, entitled “11a/g/n/acPPDU, DYNAMIC CCA AND BACKOFF,” the disclosure of which is herebyexpressly incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to communication networks and,more particularly, to wireless local area networks that utilizeorthogonal frequency division multiplexing (OFDM).

BACKGROUND

The Institute for Electrical and Electronics Engineers (IEEE) 802.11family of Standards (generally “802.11”) has gone through severaliterations over the last decade. In some of the 802.11 standards, suchas 802.11ah and beyond, the identity of the Basic Service Set (BSS)(e.g., as managed by an access point (AP) of the BSS) is indicated in aPhysical Layer Convergence Procedure (PLCP) Protocol Data Unit (PPDU) bya set of bits that described the “color” of the BSS. The color of a BSScorresponds to an identifier (ID) of the BSS that is shorter than a BSSidentifier (BSSID) defined by 802.11. The BSS color may be contained inthe Physical Layer (PHY) Signal (SIG) field in a PHY header of a PPDU,whereas the BSSID is typically included in a media access control (MAC)portion of PPDUs. A device (e.g., an AP or client) in a BSS candetermine whether a PPDU is from the BSS to which the device belongs(the “same-BSS”) or some other BSS (e.g., an overlapping BSS (OBSS)) bydecoding the SIG field and interpreting BSS color bits included therein.

One of the newer implementations of 802.11 being discussed is 802.11ax(sometimes referred to as 802.11 HE or 802.11 HEW). 802.11axcontemplates dynamically adjusting the energy level at which a channelis deemed to be clear depending on whether the energy corresponds tosame-BSS signals or to signals from another BSS. Such a scheme helps topromote spatial reuse between neighboring networks.

SUMMARY

In an embodiment, a method is carried out on a device capable ofutilizing a high efficiency wireless local area network (HEW or HE)communication protocol and a legacy communication protocol, andincludes: wirelessly receiving a communication frame; when the measuredenergy level of the frame exceeds a static clear channel assessment(CCA) energy level, identifying the BSS to which the frame corresponds,wherein identifying the BSS to which the frame corresponds includesutilizing a BSS identifier included in the frame when the frame is anHEW frame, or utilizing a MAC address included in the frame when theframe is a legacy frame; when the frame corresponds to the same BSS asthe device, processing the frame utilizing the static CCA energy level;and when the frame corresponds to an OBSS, processing the frameutilizing a dynamic CCA energy level.

In an embodiment, a method is carried out on a device capable ofutilizing an HEW communication protocol and a legacy communicationprotocol, and includes: determining that a shared wireless communicationmedium is idle based on a static CCA level; counting down in a backoffprocedure based on the determination; wirelessly receiving acommunication frame; measuring the energy level of the frame; when themeasured energy level of the frame exceeds the static CCA energy level,ceasing to count down in the backoff procedure; identifying the BSS towhich the frame corresponds; and when the frame corresponds to an OBSSand the energy of the frame is lower than a dynamic CCA energy level,resuming the countdown.

In an embodiment, a method is carried out on a wireless device andincludes forming a frame according to a wireless communication protocol,wherein the public action frame includes a BSS identifier indicatingthat the frame is a public action frame; and wirelessly transmitting theframe.

In an embodiment a wireless device is configured to perform one or moreof the above-described methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example wireless local area network(WLAN), according to an embodiment.

FIG. 2 is a diagram of communication frame, according to an embodiment.

FIG. 3 is a diagram of an example PHY data unit, according to anembodiment.

FIG. 4 is a diagram of an example multi-user PHY data unit, according toan embodiment.

FIG. 5A is a diagram of multiple legacy A-MPDUs being block-acknowledgedwith legacy block acknowledgement messages, according to an embodiment.

FIG. 5B is a diagram of multiple HEW A-MPDUs being block-acknowledgedwith legacy block acknowledgement messages, according to an embodiment.

FIG. 6A is a diagram of an HEW frame, according to an embodiment.

FIG. 6B is a diagram of a legacy frame that includes multiple MPDUs,according to an embodiment.

FIG. 6C is a diagram of a legacy frame that includes a single MPDU,according to an embodiment.

FIG. 7 is a flow diagram of an example method, according to anembodiment.

FIG. 8 is a flow diagram of an example method, according to anotherembodiment.

FIG. 9 is a flow diagram of an example method, according to stillanother embodiment.

DETAILED DESCRIPTION

In order for communication device that is compliant with a firstcommunication protocol (e.g., 802.11ax) to determine whether a giventransmission corresponds to a same-BSS or to an OBSS, the device mayobtain the BSS color from the transmission and compare the BSS color toa color of the BSS to which the device belongs. If the BSS colors arethe same, the device may conclude that the transmission corresponds tothe same-BSS. If they are different, then the device may conclude thatthe transmission corresponds to an OBSS. If the transmission correspondsto an OBSS, the device may then use dynamic CCA. However, not alltransmissions in a wireless network will necessarily have BSS colorinformation. Some transmissions, for example transmissions compliantwith a second communication protocol that is a legacy protocol (referredto herein as “legacy transmissions” or “legacy frames”), do not specifyBSS color.

According to an embodiment, a device in a wireless communication networkmay determine whether a legacy transmission corresponds to a same-BSS oran OBSS by checking a MAC address in the transmission and determiningwhether the MAC address is the same as the MAC address of the AP withwhich the device is associated. If they are the same, then the devicedetermines that the legacy transmission corresponds to the same-BSS anduses static CCA. If the MAC address in the transmission is not the sameas the MAC address of the AP, then the device determines that the legacytransmission corresponds to an OBSS and, consequently, uses dynamic CCA.

In an embodiment, certain transmissions, even if received from an OBSS,are processed using static CCA. Such transmissions include public actionframes, for example, or other suitable frames.

According to an embodiment, public action frames include a special BSScolor that is specifically reserved for public action frames.

FIG. 1 is a block diagram of example wireless local area networks(WLANs) 10-1 and 10-2, according to an embodiment. The number of WLANsdepicted is only intended to be illustrative, and any number may bepresent. Each WLAN 10 includes at least one AP 14. The configuration ofthe AP 14 may vary among different embodiments, but a typicalconfiguration will now be described, using the AP 14-1 as an example.The AP 14-1 includes a host processor 15 coupled to a network interfacedevice 16. The network interface device 16 includes a MAC processingunit 18 and PHY processing unit 20. The PHY processing unit 20 includesa plurality of transceivers 21, and the transceivers 21 are coupled to aplurality of antennas 24. Although three transceivers 21 and threeantennas 24 are illustrated in FIG. 1, the AP 14-1 includes differentnumbers (e.g., 1, 2, 4, 5, etc.) of transceivers 21 and antennas 24 inother embodiments. Although AP 14 includes the same number oftransceivers 21 and antennas 24, in other embodiments the AP 14 includesa different number of transceivers 21 than antennas 24 and antennaswitching techniques are utilized.

In various embodiments, the network interface device 16 is implementedon one or more integrated circuit (IC) devices. For example, in anembodiment, at least a portion of the MAC processing unit 18 isimplemented on a first IC device and at least a portion of the PHYprocessing unit 20 is implemented on a second IC device. As anotherexample, at least a portion of the MAC processing unit 18 and at least aportion of the PHY processing unit 20 are implemented on a single ICdevice.

Each WLAN 10 includes a plurality of client stations 25. Although twoclient stations 25 are illustrated in FIG. 1, each of the WLANs 10includes different numbers (e.g., 1, 2, 3, 5, 6, etc.) of clientstations 25 in various scenarios and embodiments.

The configuration of the client station 25 may vary among differentembodiments, but a typically configuration will now be described, usingthe client station 25-1 as an example. The client station 25-1 includesa host processor 26 coupled to a network interface device 27. Thenetwork interface device 27 includes a MAC processing unit 28 and a PHYprocessing unit 29. The PHY processing unit 29 includes a plurality oftransceivers 30, and the transceivers 30 are coupled to a plurality ofantennas 34. Although three transceivers 30 and three antennas 34 areillustrated in FIG. 1, the client station 25-1 includes differentnumbers (e.g., 1, 2, 4, 5, etc.) of transceivers 30 and antennas 34 inother embodiments. Although the client station 25-1 includes the samenumber of transceivers 30 and antennas 34, in other embodiments theclient station 25-1 includes a different number of transceivers 30 thanantennas 34 and antenna switching techniques are utilized.

In various embodiments, the network interface device 27 is implementedon one or more IC devices. For example, in an embodiment, at least aportion of the MAC processing unit 28 is implemented on a first ICdevice and at least a portion of the PHY processing unit 29 isimplemented on a second IC device. As another example, at least aportion of the MAC processing unit 28 and at least a portion of the PHYprocessing unit 29 are implemented on a single IC device.

In an embodiment, one or more of the other client stations of the WLANs10 have a structure the same as or similar to the client station 25-1.In these embodiments, the client stations 25 structured like the clientstation 25-1 have the same or a different number of transceivers andantennas. For example, the client station 25-2 has only two transceiversand two antennas (not shown), according to an embodiment. These samevariations may be present in the client stations 25 of the second WLAN10-2.

In an embodiment, each AP 14 is configured to operate according to awireless communication protocol that utilizes Orthogonal FrequencyMultiple Division Access (OFDMA) technology and/or multi-user multipleinput, multiple output (MU-MIMO) technology.

In an embodiment, each AP 14 (e.g., the network interface device 16 ofthe AP 14) is configured to transmit independent data simultaneously tomultiple client stations 25 via different spatial streams (e.g.,downlink (DL) MU-MIMO) and/or via different OFDM sub-channels (e.g., DLOFDMA). In an embodiment, the AP 14 (e.g., the network interface device16 of the AP 14-1) is configured to receive independent datasimultaneously from multiple client stations 25 via different spatialstreams (e.g., uplink (UL) MU-MIMO) and/or via different OFDMsub-channels (e.g., UL OFDMA). In some embodiments, two or more of theclient stations 25 are configured to receive respective data streamsthat are transmitted simultaneously by the AP 14 (e.g., DL OFDMA and/orDL MU-MIMO). For example, in one embodiment, the network interfacedevice 27 is configured to receive a data stream among a plurality ofindependent data streams transmitted simultaneously by the AP 14 tomultiple client stations 25 via different spatial streams and/or viadifferent OFDM sub-channels. In other embodiments, two or more of theclient stations 25 additionally or alternatively are configured totransmit corresponding data streams to the AP 14 such that the AP 14receives the data streams simultaneously (e.g., UL OFDMA and/or ULMU-MIMO). For example, in one embodiment, the network interface device27 is configured to transmit a data stream while one or more otherclient stations 25 transmit one or more other independent data streamstransmitted simultaneously to the AP 14 via different spatial streamsand/or via different OFDM sub-channels.

In an embodiment, the AP 14 and the client stations 25 contend forcommunication medium using carrier sense multiple access with collisionavoidance (CSMA/CA) protocol or another suitable medium access protocol.In an embodiment, the AP 14 and the client stations employ a CCAprocedure, in which the AP/client station determines the energy level ofthe medium in order to determine whether the medium is busy or idle. Ifthe medium is idle, the device can count down the backoff counter. Ifthe backoff counter reaches a predetermined number (e.g., 0), the devicecan transmit. If the medium is busy, the device waits until the mediumis idle and then counts down the backoff counter while the medium isidle. A threshold energy level for determining whether the medium isidle or busy may depend upon the bandwidth of the channel being used bythe device and on whether the energy corresponds to a transmission thatconforms to the wireless communication protocol. For example, in 802.11,if the channel bandwidth is 20 Megahertz (MHz), the threshold level is−82 decibel-milliwatts (dBm) for energy from valid 802.11 transmissions.For channel bandwidths of 40 MHz, 80 MHz, and 160 MHz, the thresholdlevels are −79 dBm, −76 dBm, and −73 dBm, respectively. Using theselevels for CCA is referred to herein as a “static CCA” procedure. Forenergy not identified by the device as a valid 802.11 signal, thethreshold level is −62 dBm.

In an embodiment, the AP 14 and the client stations 25 may also employ adynamic CCA procedure. In the dynamic CCA procedure, the AP/clientstation may use a higher threshold level for valid 802.11 signals froman OBSS as compared to the threshold level for valid 802.11 signals fromthe same BSS. For example, an AP/client station might deem a 20 MHzchannel to be idle if the energy level of an 802.11 signal from anotherBSS is less than −62 dBm (i.e., the same threshold level as for energycorresponding to signals that are not valid 802.11 signals), but deemthe channel to be busy if the energy level of an 802.11 signal from thesame BSS is greater than −82 dBm. Thus, an energy level of −70 dBm of avalid 802.11 signal from a different BSS would result in the devicedetermining that the channel is idle, while an energy level of −70 dBmresulting from same-BSS signals would result in the device determiningthat the channel is busy. Allowing a higher CCA level for transmissionscorresponding to another BSS helps to promote spatial reuse betweendifferent BSSs, at least in some embodiments and/or scenarios.

Further, in an embodiment, the AP 14 or a client station 25 dynamicallyselects a bandwidth for a transmission based on channels available forthe transmission. In some embodiments, communication between the AP 14and the client stations 25 can occur in a primary channel of the WLAN10, in both a primary and a secondary channel of the WLAN 10,exclusively on a secondary channel of the WLAN 10, etc. The AP mayassign the primary and the non-primary communication channels in anysuitable manner to the one or more client stations, in variousembodiments. In an embodiment, the AP 14 is configured to transmitdifferent independent data to different client stations 25simultaneously by generating an OFDMA data unit that includes differentindependent data modulated in respective sub-channels of a communicationchannel. In an embodiment, each sub-channel includes one or moresub-channel blocks, each sub-channel block corresponding to a set ofsub-carriers within the OFDMA data unit. In an embodiment, the AP 14allocates different sub-channels to different client stations andgenerates the OFDMA data unit that respective data is modulated insub-channel blocks corresponding to the sub-channels allocated to theclient stations.

FIG. 2 is a diagram of an example communication frame, designated asPPDU 200, that a device of the WLAN 10 (either AP 14 or client station25) generates and transmits according to an embodiment. The PHY protocoldata unit (PPDU) includes a PHY preamble 202, a PHY header 204, and aMAC protocol data unit (MPDU) 206. The MPDU 206 includes a Frame Controlfield 208, a Duration/ID field 210, an Address 1 field 212, and Address2 field 214, an Address 3 field 216, a Sequence Control field 218, anAddress 4 field 220, a Quality of Service (QoS) Control field 222, ahigh throughput (HT) Control field 224, a Frame Body field 226, and aframe check sequence (FCS) field 228. The Frame Control field 208includes one or more Distribution System (DS) bits, including a To DSbit and a From DS bit.

If the PPDU 200 is compliant with a first communication protocol, suchas 802.11ax, then the PHY preamble 202 includes a BSS color field (e.g.,in a signal (SIG) field) having an identifier of the BSS to which thePPDU 200 corresponds, in an embodiment. If the PPDU 200 is a compliantwith a protocol other than a first communication protocol, such as802.11a, 802.11n, 802.11ac, etc., then the PHY preamble 202 does notinclude a BSS color field, in some embodiments.

FIG. 3 is a diagram of an OFDM PHY data unit 300, according to anembodiment. In some embodiments, an AP (e.g., the AP 14) is configuredto generate and transmit OFDM PHY data units having a format such asillustrated in FIG. 3 to client stations (e.g., client stations 25),and/or a client station (e.g., the client station 25-1) is configured totransmit the data unit 300 to the AP (e.g., the AP 14). The PHY dataunit 300 conforms to the first communication protocol (e.g., the HEWprotocol) and occupies an 80 MHz band. In other embodiments, data unitssimilar to the PHY data unit 300 occupy different suitable bandwidthssuch as 20 MHz, 40 MHz, 120 MHz, 160 MHz, or any other suitablebandwidth. The PHY data unit 300 is suitable for “mixed mode”situations, such as when a WLAN 10 includes a client station thatconforms to a legacy protocol, but not the HEW protocol. The PHY dataunit 300 can be utilized in other situations as well.

The PHY data unit 300 includes a PHY preamble having four legacy shorttraining fields (L-STFs) 305; four legacy long training fields (L-LTFs)310; four legacy signal fields (L-SIGs) 315; four first high efficiencyWLAN signal fields (HEW-SIGAs) 320; four second high efficiency WLANsignal fields (HEW-SIGBs) 322; a high efficiency WLAN short trainingfield (HEW-STF) 325; and N high efficiency WLAN long training fields(HEW-LTFs) 330, where N is a suitable positive integer. The data unit300 also includes a high efficiency WLAN data portion (HEW-DATA) 340.The L-STFs 305, the L-LTFs 310, and the L-SIGs 315 form a legacy portionof the PHY preamble. The HEW-SIGA 320, the HEW HEW-SIGBs 322; theHEW-STF 325, and the HEW-LTFs 330 form a high efficiency WLAN (HEW)portion of the PHY preamble. In an embodiment, a color field is includedin the HEW-SIGAs 320. In another embodiment, the color field is includedin the HEW-SIGBs 322.

Each of the L-STFs 305, each of the L-LTFs 310, each of the L-SIGs 315,each of the HEW-SIGAs 320, and each of the HEW-SIGBs 322 occupy a 20 MHzband, in one embodiment. The data unit 300 is described as having an 80MHz contiguous bandwidth for the purposes of illustrating an exampleframe format, but such frame format is applicable to other suitablebandwidths (including noncontiguous bandwidths). For instance, althoughthe preamble of the data unit 300 includes four of each of the L-STFs305, the L-LTFs 310, the L-SIGs 315, the HEW-SIGAs 320, and theHEW-SIGBs 322 in other embodiments in which an OFDM data unit occupies acumulative bandwidth other than 80 MHz, such as 20 MHz, 40 MHz, 120 MHz,160 MHz, etc., a different suitable number of the L-STFs 305, the L-LTFs310, the L-SIGs 315, the HEW-SIGAs 320, and the HEW-SIGBs 322 areutilized accordingly. For example, for an OFDM data unit occupying a 20MHz cumulative bandwidth, the data unit includes one of each of theL-STFs 305, the L-LTFs 310, the L-SIGs 315, the HEW-SIGAs 320, and theHEW-SIGBs 322; a 40 MHz bandwidth OFDM data unit includes two of each ofthe fields 305, 310, 315, 320, and 322; a 120 MHz bandwidth OFDM dataunit includes six of each of the fields 305, 310, 315, 320, and 322; a160 MHz bandwidth OFDM data unit includes eight of each of the fields305, 310, 315, 320, and 322, and so on, according to some embodiments.

In the example PHY data unit 300, each of the HEW-STF 325, the HEW-LTFs330, and the HEW-DATA 340 occupy the entire 80 MHz cumulative bandwidthof the data unit 300. Similarly, in the case of an OFDM data unitconforming to the HEW protocol and occupying a cumulative bandwidth suchas 20 MHz, 40 MHz, 120 MHz, or 160 MHz, each of the HEW-STF 325, theHEW-LTFs 330, and the HEW-DATA 340 occupy the corresponding entirecumulative bandwidth of the data unit, in some embodiments.

In some embodiments, the 80 MHz band of the data unit 300 is notcontiguous, but includes two or more smaller bands, such as two 40 MHzbands, separated in frequency. Similarly, for other OFDM data unitshaving different cumulative bandwidths, such as a 160 MHz cumulativebandwidth, in some embodiments the band is not contiguous in frequency.Thus, for example, the L-STFs 305, the L-LTFs 310, the L-SIGs 315, theHEW-SIGAs 320, and the HEW-SIGBs 322 occupy two or more bands that areseparated from each other in frequency, and adjacent bands are separatedin frequency by at least one MHz, at least five MHz, at least 10 MHz, atleast 20 MHz, for example, in some embodiments.

According to an embodiment, each of the L-STFs 305 and each of theL-LTFs 310 have a format as specified in a legacy protocol such as theIEEE 802.11a Standard, the IEEE 802.11n Standard, and/or the IEEE802.11ac Standard. In an embodiment, each of the L-SIGs 315 has a formatat least substantially as specified in legacy protocol (e.g., the IEEE802.11a Standard, the IEEE 802.11n Standard, and/or the IEEE 802.11acStandard). In such embodiments, the length and rate subfields in theL-SIGs 315 is set to indicate a duration T corresponding to theremainder of the data unit 300 after the legacy portion. This permitsclient stations that are not configured according to the HEW protocol todetermine an end of the data unit 300 for CSMA/CA purposes, for example.For example, legacy client stations determine the duration of theremainder of the data unit 300 and refrain from accessing the medium (orat least transmitting in the medium) for the duration of the remainderof the data unit 300, in an embodiment. In other embodiments, each ofthe L-SIGs 315 has a format at least substantially as specified inlegacy protocol (e.g., the IEEE 802.11a Standard, the IEEE 802.11nStandard, and/or the IEEE 802.11ac Standard) but with length field inthe L-SIGs 315 set to indicate a duration of the time remaining in atransmission opportunity during which the data unit 300 is transmitted.In such embodiments, client stations that are not configured accordingto the HEW protocol determine an end of the transmission opportunity(TXOP) and refrain from accessing the medium (or at least transmittingin the medium) for the duration of the TXOP, in an embodiment.

In the PHY data unit 300, frequency domain symbols of the legacy portionare repeated over four 20 MHz subbands of the 80 MHz band. Legacy clientstations that are configured to operate with 20 MHz bandwidth willrecognize a legacy preamble in any of the 20 MHz subbands. In someembodiments, the modulations of the different 20 MHz subband signals arerotated by different suitable angles. In one example, a first subband isrotated 0 degrees, a second subband is rotated 90 degrees, a thirdsubband is rotated 180 degrees, and a fourth subband is rotated 270degrees, in an embodiment. In other examples, different suitablerotations are utilized. As just one example, a first subband is rotated45 degrees, a second subband is rotated 90 degrees, a third subband isrotated −45 degrees, and a fourth subband is rotated −90 degrees, in anembodiment.

In some embodiments, the modulations of the HEW-SIGAs 320 in thedifferent 20 MHz subbands is rotated by different angles. In oneexample, a first subband is rotated 0 degrees, a second subband isrotated 90 degrees, a third subband is rotated 180 degrees, and a fourthsubband is rotated 270 degrees, in an embodiment. In other examples,different suitable rotations are utilized. As just one example, a firstsubband is rotated 45 degrees, a second subband is rotated 90 degrees, athird subband is rotated −45 degrees, and a fourth subband is rotated−90 degrees, in an embodiment. In an embodiment, the same rotationsutilized in the legacy portion are utilized for the HEW-SIGAs 320. Insome embodiments, the modulations of the HEW-SIGBs 322 in the different20 MHz subbands are similarly rotated by different angles. In at leastsome examples, the HEW-SIGAs 320 are collectively referred to as asingle HEW signal field (HEW-SIGA) 320. In at least some examples, theHEW-SIGBs 322 are collectively referred to as a single HEW signal field(HEW-SIGB) 322.

In an embodiment, the PHY data unit 300 is a single user data unit thatincludes data for only a single AP or only a single client station 25.In another embodiment, the data unit 300 is a multi-user data unit thatincludes independent data streams for multiple client stations 25 overrespective spatial streams. In an embodiment in which the PHY data unit300 is a multi-user data unit, a portion of the data unit 300 (e.g., theL-STFs 305, the L-LTFs 310, the L-SIGs 315, the HEW-SIGAs 320, and theHEW-SIGBs 322) is unsteered or omnidirectional (or “omnidirectional” or“pseudo-omnidirectional”; the terms “unsteered” and “omnidirectional” asused herein are intended to also encompass the term“pseudo-omnidirectional”) and includes data that is common to allintended recipients of the data unit 300. The data unit 300 furtherincludes a second portion (e.g., the HEW-STF 325, the HEW-LTFs 330, andthe HEW-DATA portion 340) in which beamforming is applied to differentspatial streams to shape, or beamform, transmission over thecorresponding spatial streams to particular client stations 25. In somesuch embodiments, the steered portion of the data unit 300 includesdifferent (e.g., “user-specific”) content transmitted over differentspatial streams to different ones of the client stations 25.

In some embodiments, the AP 14 is configured to transmit respective OFDMdata units, such as the OFDM data unit 300, simultaneously to multipleclient stations 25 as parts of a downlink OFDMA transmission from the AP14 to the multiple client stations 25. In an embodiment, the AP 14transmits the respective OFDM data units in respective sub-channelsallocated to the client stations. Similarly, in an embodiment, multipleclient stations 25 transmit respective OFDM data units, such as the OFDMdata unit 300, simultaneously to the AP 14 as parts of an uplink OFDMAtransmission from the multiple client stations 25 to the AP 14. In anembodiment, the client stations 25 transmit the respective OFDM dataunits in respective sub-channels allocated to the client stations 25.

In some embodiments, the uplink data units (e.g., transmitted from aclient station to an AP) omit HEW-SIGBs. For instance, in someembodiments, the AP instructs client stations regarding which parameters(e.g., MCS, number of spatial streams, etc.) to use when transmitting tothe AP, and thus such parameters need not be included in the PHYpreamble of uplink data units. Thus, this allows omission of theHEW-SIGBs from uplink data units.

In some embodiments, SU data units omit HEW-SIGBs. For instance, in someembodiments, some parameters in the HEW-SIGB relate to multi-usertransmissions, and other parameters (e.g., MCS, number of spatialstreams, etc.) in the HEW-SIGB can be included in the HEW-SIGA. Thus,this allows omission of the HEW-SIGBs from SU data units.

In some embodiments, the HEW-SIGB(s) are positioned after the HEW-LTFs330. In such embodiments, the HEW-SIGB(s) occupy the entire cumulativebandwidth of the data unit 300. For example, in the case of an OFDM dataunit conforming to the HEW protocol and occupying a cumulative bandwidthsuch as 20 MHz, 40 MHz, 120 MHz, or 160 MHz, the HEW-SIGB(s) thecorresponding entire cumulative bandwidth of the data unit, in someembodiments. In such embodiments, beamforming is applied to differentspatial streams to shape, or beamform, HEW-SIGBs over the correspondingspatial streams to particular client stations 25.

In some embodiments, further SIG fields are included in the PHY preambleand positioned after the HEW-LTFs 330. In such embodiments, beamformingis applied to different spatial streams to shape, or beamform, thefurther SIG fields over the corresponding spatial streams to particularclient stations 25.

FIG. 4 is a diagram of an example OFDMA PHY data unit 400, according toan embodiment. The OFDMA PHY data unit 400 includes a plurality of OFDMPHY data units 402. Respective ones of the PHY data units 402 includeindependent data streams transmitted to, or received from, respectiveones of two client stations 25. In an embodiment, each OFDM PHY dataunit 402 is the same as or similar to the OFDM PHY data unit 300 of FIG.3. In an embodiment, the AP 14 transmits the OFDM PHY data units 402 todifferent client stations 25 via respective OFDM sub-channels within acomposite channel spanned by the OFDMA PHY data unit 400. In anotherembodiment, different client stations 25 transmit respective OFDM PHYdata units 402 to the AP 14 in respective OFDM sub-channels within thecomposite channel spanned by the OFDMA PHY data unit 400. In such anembodiment, the AP 14 receives the OFDM PHY data units 402 from theclient stations 25 via respective OFDM sub-channels of within thecomposite channel spanned by the OFDMA PHY data unit 400. Although thePHY data unit 400 is illustrated in FIG. 4 as including only two PHYdata units 402 transmitted to, or received from, only two clientstations 25, the PHY data unit 400 includes more than two (e.g., 3, 4,5, 6, etc.) PHY data units 402 transmitted to, or received from, morethan two (e.g., 3, 4, 5, 6, etc.) client stations 25, in otherembodiments.

Each of the OFDM PHY data units 402 conforms to a communication protocolthat defines OFDMA communication, such as the HEW communicationprotocol, in an embodiment. In an embodiment in which the OFDMA PHY dataunit 400 corresponds to a DL OFDMA data unit, the OFDMA PHY data unit400 is generated by the AP 14 such that each OFDM PHY data unit 402 istransmitted to a respective client station 25 via a respectivesub-channel allocated for downlink transmission of the OFDMA PHY dataunit 400 to the client station. Similarly, an embodiment in which theOFDMA PHY data unit 400 corresponds to an UL OFDMA data unit, the AP 14receives the OFDM PHY data units 402 via respective sub-channelsallocated for uplink transmission of the OFDM PHY data units 402 fromthe client stations, in an embodiment. For example, the OFDM PHY dataunit 402-1 is transmitted via a first 40 MHz sub-channel, and the OFDMPHY data unit 402-2 is transmitted via a second 40 MHz sub-channel, inan embodiment.

In an embodiment, each of the OFDM PHY data units 402 includes apreamble including one or more L-STFs 404, one or more L-LTFs 406, oneor more L-SIGs 408, one or more HEW-SIG-As 410, N HEW-LTFs, and aHEW-SIGB 414. Additionally, each OFDM PHY data unit 402 includes aHEW-DATA portion 418. In an embodiment, each L-STF field 404, each L-LTFfield 406, each L-SIG field 408, each HEW-SIGA field 410, and eachHEW-SIGB field 411 occupies a smallest channel bandwidth supported bythe WLAN 10 (e.g., 20 MHz). In an embodiment, if an OFDM data unit 402occupies a bandwidth that is greater than the smallest channel bandwidthof the WLAN 10, then each L-STF field 404, each L-LTF field 406, eachL-SIG field 408, each HEW-SIGA field 410, and each HEW-SIGB field 411 isduplicated in each smallest channel bandwidth portion of the OFDM dataunit 402 (e.g., in each 20 MHz portion of the data unit 402). On theother hand, each HEW-STF field 412, each HEW-LTF field 414, and each HEWdata portion 418 occupies an entire bandwidth of the corresponding OFDMdata unit 402, in an embodiment.

In an embodiment, padding is used in one or more of the PHY OFDM dataunits 402 to equalize lengths of the OFDM data units 402. Accordingly,the length of each of the OFDM PHY data units 402 correspond to thelength of the OFDMA PHY data unit 402, in this embodiment. Ensuring thatthe OFDM data units 402 are of equal lengths facilitates synchronizingtransmission of acknowledgment frames by client stations 25 that receivethe PHY data units 402, in an embodiment. In an embodiment, each of oneor more of the OFDM PHY data units 402 includes an aggregate MACprotocol data unit (A-MPDU) (e.g., a very high throughput (VHT) A-MPDUthat includes multiple aggregated VHT MAC protocol data units (MPDUs),an HEW A-MPDU that includes multiple aggregated HEW MPDUs, or anothersuitable aggregated data unit that includes multiple MPDUs), which is inturn included in a PPDU. In another embodiment, each of one or more ofthe OFDM data units 402 includes a single MPDU (e.g., a single VHT MPDU,a single HEW MPDU, or another suitable non-aggregated MPDU), which is inturn included in a PPDU. In an embodiment, padding (e.g., zero-padding)within one or more of the A-MPDUs 402 or single MPDUs 402 is used toequalize the lengths of the PHY data units 402.

In an embodiment, the AP 14 forms groups of client stations 25 forsimultaneous downlink transmissions to client stations 25 and/orsimultaneous uplink transmissions by client stations 25. To this end,the AP 14 allocates respective sub-channels to client stations 25 withina group of client stations 25 and/or allocates respective spatialstreams to client stations 25, in embodiments. In an embodiment and/orscenario, the AP 14 then transmits one or more OFDMA PHY data units tothe client stations 25 in a group using the respective sub-channelsallocated to the client stations 25 within the group and/or transmitsone or more MU MIMO data units to client stations 25 in a group usingrespective spatial streams allocated to the client stations 25 withinthe group. Each group of client stations 25 includes two or more clientstations 25, in an embodiment. A particular client station 25 belongs toone or more groups of the client stations 25, in an embodiment. Thus,for example, a first group of client stations 25 includes the clientstation 25-1 and the client station 25-2, and a second group of clientstations 25 includes the client station 25-1 and the client stations25-3, in an example embodiment and/or scenario. Accordingly, the clientstation 25-1 belongs to the first group of client stations 25 and to thesecond group of client stations 25, in this example embodiment and/orscenario. In an embodiment, the AP dynamically select the members of aMU transmission.

In an embodiment, a color field is included in the HEW-SIGAs 410. Inanother embodiment, the color field is included in the HEW-SIGBs 411.

In some embodiments, UL OFDMA PHY data units (e.g., transmitted from aclient station to an AP) omit HEW-SIGBs. For instance, in someembodiments, the AP instructs client stations regarding which parameters(e.g., MCS, number of spatial streams, etc.) to use when transmitting tothe AP, and thus such parameters need not be included in the PHYpreamble of uplink data units. Thus, this allows omission of theHEW-SIGBs from UL OFDMA PHY data units.

In some embodiments, the HEW-SIGBs are positioned after the HEW-LTFs414. In such embodiments, each HEW-SIGB 411 occupies an entire bandwidthof the corresponding OFDM data unit 402. In such embodiments,beamforming is applied to different spatial streams to shape, orbeamform, HEW-SIGBs 411 over the corresponding spatial streams toparticular client stations 25.

In some embodiments, further SIG fields are included in the PHY preambleand positioned after the HEW-LTFs 330. In such embodiments, beamformingis applied to different spatial streams to shape, or beamform, thefurther SIG fields over the corresponding spatial streams to particularclient stations 25.

According to an embodiment, a device (AP or client station) of a WLAN 10may be capable of transmitting a public action frame. Public actionframes are used to communicate globally (e.g., both within the BSS ofthe AP and to neighboring BSSs), and are intended to be received bydevices both within and without the BSS with which they originate.Illustrative examples of public action frames include GenericAdvertisement Service (GAS) and Fine Timing Measurement (FTM) frames.Besides public action frames, management frames (e.g., a proberequest/response and association request/response) may also betransmitted outside of a BSS. If a device uses a dynamic CCA level forthe reception of a public action frame or a management frame sentoutside of a BSS, the public action/management frame may be improperlydiscarded. In order to address this issue, in an embodiment, devices ina WLAN 10 that are capable of employing dynamic CCA may refrain fromusing dynamic CCA when receiving a public action frame or a managementframe sent outside of a BSS.

In an embodiment, one or more of the client stations 25 is not capableof using a wireless communication protocol that recognizes BSS colors.For example, one or more of the client stations 25 may use a legacy802.11 protocol. Such a client station may still, however, associatewith an 802.11ax-capable AP 14. Furthermore, an 802.11ax-capable AP 14may communicate using a legacy 802.11 protocol, e.g. Ack/BA frame in11a/g PPDU for TXOP protection. As a result, communication within a WLAN10 may take the form of, for example, a first device transmitting using802.11ax and a second device responding (e.g., with an ACK) using alegacy 802.11 wireless communication protocol. For example, FIG. 5Aillustrates communication between devices of a WLAN, in which one of thedevices transmits an 802.11a block acknowledge (BA) 506 to acknowledge aVHT data PPDU 500, a BA 508 to acknowledge a High Throughput (HT) dataPPDU 502, and a BA 510 to acknowledge an HT data PPDU 504. Similarly,FIG. 5B illustrates communication between devices of a WLAN, in whichone of the devices transmits an 802.11a BA 518 to acknowledge an HEWdata PPDU 512, a BA 520 to acknowledge an HEW data PPDU 514, and a BA522 to acknowledge an HEW data PPDU 516.

In an embodiment, when a device (AP 14 or client station 25) of a WLAN10 that is capable of communicating using 802.11ax receives a legacyPPDU, the device uses a normal CCA level and (a) determines whether thePPDU corresponds to self-BSS or OBSS, and (b) determines (based on therecipient address contained within the PPDU) whether the device is theproper recipient of the PPDU. For example, in some embodiments, if thedevice determines that the received PPDU has an energy level that is atleast as high the normal CCA level, the device carries out one or moreof the following processes:

(1) Check the Address 1 field (FIG. 2); if Address 1 is same as the MACaddress of the device, the device acts as the TXOP responder.

(2) Check the To DS bit (in the Frame Control field, FIG. 2); if Address1 of the decoded data frame is the MAC address of the AP 14 with whichthe device is associated, and the To DS is 1, the device determines thatPPDU corresponds to same-BSS.

(3) Check the From DS bit (in the Frame Control, FIG. 2); if Address 2of the decoded data frame is the MAC address of the associated AP 14 andthe From DS is 1, the device determines that the PPDU corresponds tosame-BSS.

(4) If the decoded frame has two MAC addresses (e.g., the frame is acontrol frame) and one of them is the MAC address of the associated AP14, the device determines that the PPDU corresponds to same-BSS.

(5) If the decoded frame (e.g., a control frame) is used to acknowledgea MPDU/A-MPDU from the same-BSS, the device determines that PPDUcorresponds to same-BSS.

(6) If the frame is a management frame and one of Address 1 and Address2 of the decoded management frame is the MAC address of the associatedAP 14, then the device determines that the PPDU corresponds to same-BSS.

(7) If the decoded management frame is a public action frame forinter-BSS operation or for association, the device sets the networkallocation vector (NAV) in accordance with the received Duration/IDfield (FIG. 2) if the value of the received Duration/ID field is biggerthan the value of the NAV timer.

(8) If the device cannot correctly decode the PPDU, then the deviceprocesses the PPDU as if it corresponds to same-BSS.

(9) If none of conditions 1-8 above apply, then the device determinesthat the PPDU corresponds to OBSS.

(10) When the PPDU corresponds to same-BSS and the device is not theTXOP responder, the device sets the NAV in accordance with the receivedDuration/ID field if the value of the received Duration/ID field isbigger than the value of the NAV timer.

(11) When the PPDU corresponds to OBSS, the device sets the NAV inaccordance with the received Duration/ID field if the value of thereceived Duration/ID field is bigger than the value of the NAV timer andthe receive power of the PPDU is same as or higher than the dynamic CCAlevel.

In an embodiment, a device (either AP 14 or client station 25) of a WLAN10 behaves in the role of TXOP holder or TXOP responder as follows.After a TXOP holder sends a first PPDU of the TXOP to the TXOPresponder, the TXOP holder uses normal CCA level to determine whetherthe medium is busy or not and decodes MPDUs until the end of the TXOP.After the first successful frame exchange, the TXOP responder usesnormal CCA level to decide whether the medium is busy or not and decodesMPDUs until the end of the TXOP.

In an embodiment, a device (either AP 14 or client station 25) of a WLAN10 transmits and receives public action frames and association frames asfollows. A broadcast BSS color is used for i) an HEW PPDU that carriesinter-BSS frames and ii) frames for communication between an AP 14 andunassociated client station 25. If the broadcast BSS color is notacceptable, the HEW PPDU is not allowed to carry i) inter-BSS frames orii) frames for the communication between an AP 14 and unassociatedclient station 25.

According to an embodiment, when a device (either AP 14 or clientstation 25) receives a PPDU, it carries out a backoff procedure andutilizes (if necessary) dynamic CCA as follows. Each time the channelchanges from idle to busy based on the static CCA level, the PHYprocessing unit 20 or 29 reports static CCA busy to the MAC processingunit 18 or 28 and the MAC processing unit, in response, stopsdecrementing a backoff counter. If the device is a client station 25,the PPDU is a legacy PPDU, and the device determines that the legacyPPDU corresponds to OBSS and the CCA is lower than the dynamic CCAlevel, the device again decrements the backoff counter with each idleslot an arbitration inter-frame spacing (AIFS) after the currentlydetected PPDU until the beginning of the following busy indication basedon the static CCA level. In some embodiments, idle slots are time slots,each of a given suitable duration (e.g., 9 μs, 20 μs, 50 μs, or anyother suitable duration), in which the medium is determined to be idle.If the device is a client station 25, the PPDU is an HEW PPDU, and thedevice determines that the HEW PPDU corresponds to OBSS (e.g., bychecking the BSS color) and the CCA is lower than the dynamic CCA level,the device again decrements the backoff counter with each idle slot anAIFS after the HE PPDU header until the beginning of the following busyindication based on the normal CCA level. In some embodiments, thedevice decrements the backoff counter for idle slots immediately afterthe legacy PPDU, or immediately after the HE PPDU header (e.g., ratherthan waiting the AIFS period). In some embodiments, the devicedecrements the backoff counter for each idle slot some other suitabletime period after the ending of the legacy PPDU or the ending of the HEPPDU header, such as a Point Coordination Function (PCF) InterframeSpace (PIFS) period.

FIG. 6A is a diagram of an HE PPDU, FIG. 6B is a diagram of a legacyPPDU that includes an A-MPDU having multiple MPDUs, and FIG. 6C is adiagram of a legacy PPDU that includes a single MPDU. To carry out abackoff procedure according to an embodiment during receipt of each ofthese types of PPDUs in an embodiment, a device (either AP 14 or clientstation 25) uses a static CCA procedure to determine if the medium isbusy, and then performs the following actions. At time t0, the devicedetermines that the medium is idle and decrements the backoff counter.At time t1, the device detects the PPDU and, using static CCA,determines that the medium is busy and therefore ceases decrementing thebackoff counter. At time t2, the device determines whether the PPDUcorresponds to same-BSS or to OBSS. If the PPDU is an HEW PPDU (as inFIG. 6A), then the device makes this determination based on the BSScolor (obtained from the HE PHY header). Otherwise, if the PPDU is alegacy PPDU (as in FIG. 6B), then the device makes this determination bydecoding one or more MAC addresses from the first MPDU in the PPDU(e.g., the originating MAC address). If the PPDU is determined to befrom OBSS and the energy level of the PPDU is below the dynamic CCAlevel, then the device determines the communication medium to be idle(in spite of the fact that there is still an A-MPDU being transmitted)and resumes decrementing the backoff counter for each idle slot aftertime t3 (e.g., immediately after the end of the HE PHY preamble, the endof the legacy PPDU, or the end of the first MPDU in the legacy PPDU, inan embodiment, an AIFS period after, in another embodiment, a PIFSperiod after, in another embodiment, etc.). At time t4, another PPDUbegins and the device determines that the communication medium is busybased on static CCA. In response to determining that the communicationmedium is busy, the device ceases decrementing the backoff counter.

As can be seen in FIGS. 6B and 6C, in some embodiments, because thedevice must analyze a MAC header in a legacy PPDU in order to determineif the PPDU is a same-BSS or an OBSS PPDU, the device first mustentirely receive an MPDU that includes the MAC header before informationin the MAC header can be verified. For example, in some embodiments, theMPDU utilizes error control coding (ECC), and the device uses parityinformation in the MPDU (e.g., at an end of the MPDU) to verify that theMPDU (including the MAC header) is error free and/or to correct errorsin the MPDU.

According to another embodiment, when a device (either AP 14 or clientstation 25) receives a PPDU, it carries out a backoff procedure andutilizes (if necessary) dynamic CCA as follows. Each time the channelchanges from idle to busy based on a normal CCA level, the PHYprocessing unit 20 or 29 reports static CCA busy to the MAC processingunit 18 or 28. In response, the MAC processing unit 18 or 28 stopsdecrementing the backoff counter. If the device determines that a legacyPPDU corresponds to OBSS and the CCA is lower than the dynamic CCAlevel, the device decreases the backoff counter with each idle slot fromthe beginning of the PPDU. If the backoff timer is at 0 at the time thatthe device determines that the legacy PPDU corresponds to OBSS, thedevice determines that the device can immediately access the medium. Ifthe device determines that an HEW PPDU corresponds to OBSS (e.g., byidentifying the BSS color) and the CCA is lower than the dynamic CCAlevel, the device decreases the backoff counter with each idle slot fromthe beginning of the PPDU (e.g., the beginning of the HEW PPDU, in anembodiment, or the beginning of the HEW preamble, in anotherembodiment). In some embodiments, the device decrements the backoffcounter for each idle slot a suitable time period after the start of thelegacy PPDU, after the start of the HE PPDU, or the ending of the HEPPDU header, such as an AIFS period, a PIFS period, etc.

Referring again to FIGS. 6A, 6B, and 6C, to carry out a backoffprocedure according to an embodiment during receipt of each of thesetypes of PPDUs, a device (either AP 14 or client station 25) uses astatic CCA procedure to determine if the medium is busy, and thenperforms the following actions. At time t0, the device determines thatthe medium is idle and decrements the backoff counter. At time t1, thedevice detects the PPDU and, using static CCA, determines that themedium is busy and therefore ceases decrementing the backoff counter. Attime t2, the device determines whether the PPDU corresponds to same-BSSor OBSS, either through the use of the BSS color (in the case of an HEWPPDU) or through the use of a MAC address (in the case of a legacyPPDU). If the PPDU is determined to be from OBSS and the energy level ofthe PPDU is below the dynamic CCA level, then the device decrements thebackoff counter for each idle slot from the beginning of the PPDU. Insome embodiments, the device decrements the backoff counter for eachidle slot a suitable time period after the start of the PPDU, such as anAIFS period, a PIFS period, etc.

According to another embodiment, when a device (either AP 14 or clientstation 25) receives a PPDU, the device carries out a backoff procedureand utilizes (if necessary) dynamic CCA as follows. Each time thechannel changes from idle to busy based on the normal CCA level, the PHYprocessing unit 20 or 29 reports static CCA busy to the MAC processingunit 18 or 28. In response, the MAC processing unit 18 or 28 stopsdecrementing the backoff counter. If the device determines that a legacyPPDU corresponds to OBSS and the CCA is lower than the dynamic CCAlevel, the device then decrements the backoff counter for each idle slotfrom the beginning of the PPDU. If the device determines that an HEWPPDU corresponds to OBSS (e.g., by identifying the BSS color) and theCCA is lower than the dynamic CCA level, the device decreases thebackoff counter with each idle slot from the beginning of the HEW PPDU(e.g., the beginning of the HEW PPDU, in an embodiment, or the beginningof the HEW preamble, in another embodiment). In some embodiments, thedevice decrements the backoff counter for each idle slot a suitable timeperiod after the start of the legacy PPDU, after the start of the HEPPDU, or the beginning of the HEW preamble, such as an AIFS period, aPIFS period, etc. When the backoff timer is 0 at the time that thedevice determines that a legacy PPDU corresponds to OBSS, the devicedetermines that the device has access to the medium with a probabilityof:Probability=1−REMAIN_SLOT/SLOT_NUM  Equ. 1where REMAIN_SLOT is the value of the backoff counter at the beginningof detecting the PPDU, SLOT_NUM is the number of slots from thebeginning of detecting PPDU to the time that the device determines thatthe legacy PPDU is from OBSS. For example, in an embodiment, the device(e.g., the network interface device 16, 27; the host 15, 26, the MACprocessing unit 18, 28, etc.) includes a random number generator anduses the random number generator and the probability value (e.g.,determined using Equ. 1 or another suitable equation) to determine ifthe device can access the medium. If the device loses the medium accessright at the time that the device determines that the legacy PPDUcorresponds to OBSS (e.g., if the device, using the random numbergenerator and the determined probability, determines that the devicecannot access the medium), the device resets the backoff counter valueto the backoff counter value at which the device detected the PPDU.

FIGS. 7, 8, and 9 are flow diagrams of respective example methods 700,800, and 900 according to respective embodiments. In some embodiments,one or more of the methods 700, 800, and 900 are implemented by the AP14 (FIG. 1). In other embodiments, one or more of the methods areimplemented by the client station 25. In still other embodiments, one ormore of the methods are implemented by both the AP 14 and the clientstation 25. For example, in some embodiments, the network interfacedevice 16 and/or 27 is configured to implement one or more of themethods 700, 800, and 900. As another example, in some embodiments, thehost processor 15 is configured to implement at least a portion of oneor more of the methods 700, 800, and 900. As another example, in someembodiments, the host processor 15 and/or 26 and the network interfacedevice 16 and/or 27 are configured to implement one or more of themethods 700, 800, and 900. As yet another example, in some embodiments,the MAC processors 18 and/or 28 is configured to implement portions ofone or more of the methods 700, 800, and 900, and the PHY processors 20and/or 29 are configured to implement other portions of one or more ofthe methods 700, 800, and 900. In other embodiments, another suitablecommunication device is configured to implement one or more of themethods 700, 800, and 900.

Turning to FIG. 7, at block 702, a communication frame is received. Atblock 704, a determination is made as to whether the communication frameis a valid WiFi signal. In some embodiments, the PHY processors 20and/or 29 are configured to determine whether signal is a valid WiFisignal by determining whether the signal includes a PHY preamble thatcomplies with a WiFi communication protocol. If it is determined thatthe communication frame is not a valid WiFi signal, at block 708, anenergy level of the signal is compared to a first threshold as part of aCCA procedure. The first threshold is higher than a second thresholdalso used as part of the CCA procedure, as will be described below. Insome embodiments, the PHY processors 20 and/or 29 are configured todetermine energy levels of signal, and the MAC processors 18 and/or 28,and/or the PHY processors 20 and/or 29 are configured to compare energylevels to thresholds.

On the other hand, if it is determined at block 704 that the signal is avalid WiFi signal, the flow proceeds to block 706. At block 706, the BSSto which the communication frame corresponds is identified. At block710, a determination is made as to whether the BSS to which thecommunication frame corresponds is the same as the BSS to which thedevice carrying out the method 700 corresponds. At block 712, if the BSSis the same, the energy level of the signal is compared to the secondthreshold as part of the CCA procedure, where the second threshold islower than the first threshold.

On the other hand, if it is determined at block 710 that the BSS is notthe same, then the flow proceeds to block 708, at which the energy levelof the signal is compared to the first threshold as part of a CCAprocedure.

In some embodiments, block 710 includes determining if the frame is apublic action frame. In some embodiments, if it is determined that theframe is a public action frame, the frame is processed using the lowerthreshold at block 712. In some embodiments, block 710 includesdetermining if the frame is a management frame transmitted outside of aBSS (e.g., a probe request/response and association request/response).In some embodiments, if it is determined that the frame is a managementframe transmitted outside of a BSS (e.g., a probe request/response andassociation request/response), the frame is processed using the lowerthreshold at block 712.

In some embodiments, if it is determined at block 710 that the BSS isnot the same, the energy level of the signal is compared to the thirdthreshold, where the third threshold is higher than the second thresholdbut lower than the first threshold.

Turning to FIG. 8, at block 802, a determination is made that a sharedwireless communication medium is idle based on a static CCA procedure(e.g., a signal energy level is compared to i) a first threshold if thesignal is not a valid WiFi signal or ii) a second threshold if thesignal is a valid WiFi signal, where the first threshold is higher thanthe second threshold). At block 804, a countdown in a backoff procedureis carried out based on the determination. For example, if it isdetermined at block 804 that the medium is idle, a backoff counter isdecremented, according to an embodiment. At block 806, a communicationframe is wirelessly received. At block 808, the energy level of theframe is measured. At block 810, when the energy level exceeds thestatic CCA energy level (e.g., a signal energy level is compared to i) afirst threshold if the signal is not a valid WiFi signal or ii) a secondthreshold if the signal is a valid WiFi signal, where the firstthreshold is higher than the second threshold), counting down in thebackoff procedure is ceased (e.g., decrementing the backoff counter ispaused, in an embodiment). At block 812, the BSS to which the framecorresponds is identified. At block 814, when the frame corresponds toOBSS and the energy of the frame is lower than a dynamic CCA level(e.g., the first threshold, in an embodiment, a third threshold which ishigher than the second threshold and lower than the first threshold, inanother embodiment), the countdown is resumed. For example, if it isdetermined at block 814 that the frame corresponds to OBSS and theenergy of the frame is lower than the dynamic CCA level, decrementingthe backoff counter is resumed, according to an embodiment.

In an embodiment, block 814 includes decrementing a backoff counter foreach idle slot immediately after determining the energy of the frame islower than the dynamic CCA level. In another embodiment, block 814includes decrementing a backoff counter for each idle slot apredetermined time period (e.g., AIFS) after determining the energy ofthe frame is lower than the dynamic CCA level. In another embodiment,block 814 includes decrementing a backoff counter for each idle slotafter the beginning of the PPDU. In another embodiment, block 814includes decrementing a backoff counter for each idle slot after alegacy portion of a PHY preamble of the PPDU.

In some embodiments, the method 800 further includes, if the backoffcounter is zero when it is determined at block 814 that the energy levelof a legacy PPDU of an OBSS is below the second, higher threshold, thedevice determines that the device can access the medium.

In some embodiments, the method 800 further includes, if the backoffcounter is zero when it is determined at block 814 that the energy levelof a legacy PPDU of an OBSS is below the second, higher threshold, thedevice determines a probability that the device can access the medium(e.g., using Equ. 1 or another suitable equation) and then determineswhether the device can access the medium based on the determinedprobability (e.g., using a random number generator). In an embodiment,if the device determines that the device cannot access the medium, thedevice resets the backoff counter value to the backoff counter value atwhich the device detected the PPDU and continues the backoff countdownprocedure.

In some embodiments, method 800 further includes determining if theframe is a public action frame. In some embodiments, if it is determinedthat the frame is a public action frame, the frame is processed usingthe lower threshold at block 814.

Turning to FIG. 9, at block 902, a communication frame is generated toinclude, in a PHY preamble of the communication frame, a BSS identifierindicating that the frame is a public action frame. For example, in anembodiment, the BSS identifier is a BSS color value reserved for publicaction frames. In an embodiment, the BSS identifier is included in asignal field (e.g., HE SIGA) in the PHY preamble. At block 904, thecommunication frame is wirelessly transmitted.

In some embodiments, block 902 comprises, for frames that are managementframes to be transmitted outside of a BSS (e.g., probe request/responsesand association request/responses), including, in the PHY preamble, aBSS identifier indicating that the frame is a public action frame. Insome embodiments, block 902 comprises, for frames that are managementframes to be transmitted outside of a BSS (e.g., probe request/responsesand association request/responses), including, in the PHY preamble, aBSS identifier indicating that the frame is a management frametransmitted outside of a BSS (e.g., probe request/responses andassociation request/responses).

At least some of the various blocks, operations, and techniquesdescribed above may be implemented utilizing hardware, a processorexecuting firmware instructions, a processor executing softwareinstructions, or any combination thereof. Examples of suitable hardwareinclude a microprocessor, microcontroller, one or more integratedcircuits, one or more application specific integrated circuits (ASICs),one or more field programmable gate arrays, one or more programmablelogic devices, etc. When implemented utilizing a processor executingsoftware or firmware instructions, the software or firmware instructionsmay be stored on a computer readable medium, or media, such as amagnetic disk, an optical disk, a random access memory (RAM), a readonly memory (ROM), a flash memory, a magnetic tape, etc. The software orfirmware instructions may include machine readable instructions that,when executed by one or more processors, cause the one or moreprocessors to perform various acts.

When implemented in hardware, the hardware may comprise one or more ofi) discrete components, ii) one or more integrated circuits, iii) one ormore ASICs, iv) one or more programmable logic devices, etc.

While the present disclosure has been described with reference tospecific examples, which are intended to be illustrative only and not tobe limiting of the invention, changes, additions and/or deletions may bemade to the disclosed embodiments without departing from the scope ofthe claims.

What is claimed is:
 1. A method comprising: on a communication deviceconfigured to operate according to a first wireless local area network(WLAN) communication protocol: wirelessly receiving a communicationframe; measuring an energy level of the communication frame; when themeasured energy level of the communication frame meets a static clearchannel assessment (CCA) criterion, identifying a basic service set(BSS) to which the frame corresponds, wherein identifying the BSS towhich the frame corresponds comprises i) utilizing a BSS identifierincluded in a physical layer (PHY) preamble of the communication framewhen the frame complies with the first WLAN communication protocol orii) utilizing a media access control (MAC) address included in a MAClayer header of the communication frame when the communication framecomplies with a second WLAN communication protocol that is a legacycommunication protocol; when the frame corresponds to a same BSS withwhich the communication device is associated, further processing theframe utilizing a first energy level threshold; when the frame i)corresponds to an overlapping BSS (OBSS), ii) includes a broadcast BSSidentifier or a BSS identifier reserved for public action frames, andiii) is either a public action frame or a management frame, furtherprocessing the frame utilizing the first energy level threshold; andwhen the frame corresponds to an OBSS and is not a public action frameand is not a management frame, further processing the frame utilizing asecond energy level threshold that is higher than the first energy levelthreshold.
 2. The method of claim 1, wherein: the communication frame isa data frame; wherein the MAC address is one of a plurality of MACaddresses contained in the MAC layer header of the data frame; and themethod further comprises utilizing a distribution system (DS) value inthe data frame to determine which of the plurality of MAC addresses isthe MAC address of an access point (AP) associated with the data frame.3. The method of claim 2, further comprising determining that the dataframe corresponds to the same BSS with which the communication device isassociated when the MAC address of the AP in the MAC layer header is asame MAC address of an AP with which the communication device isassociated.
 4. The method of claim 1, wherein: the communication frameis a control frame or a management frame; the MAC layer header of thecommunication frame includes a plurality of MAC addresses; and utilizinga MAC address included in the MAC layer header of the communicationframe comprises determining that the communication frame corresponds tothe same BSS with which the communication device is associated when anyof the plurality of MAC addresses included in MAC layer header of thecommunication frame is a same MAC address of an AP with which thecommunication device is associated.
 5. The method of claim 1, whereinthe communication frame is a control frame, the method furthercomprising: determining whether the control frame corresponds to thesame BSS with which the device is associated based on whether thecontrol frame is used to acknowledge a data unit transmitted in the BSSwith which the device is associated.
 6. The method of claim 1, whereinthe communication frame includes a duration field in the MAC layerheader, the method further comprising: when i) the frame corresponds tothe BSS with which the communication device is associated and ii) thecommunication device is not a transmission opportunity (TXOP) responder,setting a network allocation vector (NAV) timer according to theduration field if a value in the duration field is larger than the valueof the NAV timer.
 7. The method of claim 1, wherein the communicationframe includes a duration field in the MAC layer header, the methodfurther comprising: when the frame corresponds to the OBSS, setting anetwork allocation vector (NAV) timer according to the duration field ifa value in the duration field is larger than the value of the NAV timerand the measured energy level of the communication frame is equal to orgreater than the second energy level threshold.
 8. A method comprising:on a communication device configured to operate according to a firstwireless local area network (WLAN) communication protocol: determiningthat a shared wireless communication medium is idle based on a staticclear channel assessment (CCA) criterion; in response to determiningthat the shared wireless communication medium is idle, counting down atimer in a backoff procedure; wirelessly receiving a communicationframe; measuring an energy level of the communication frame; when themeasured energy level of the communication frame meets the static CCAcriterion, pausing counting down the timer in the backoff procedure;identifying a basic service set (BSS) to which the communication framecorresponds; when the communication frame corresponds to a same BSS withwhich the communication device is associated, and the energy of thecommunication frame is lower than a first energy level threshold,resuming counting down the timer in the backoff procedure; when thecommunication frame i) corresponds to an overlapping BSS (OBSS), ii)includes a broadcast BSS identifier or a BSS identifier reserved forpublic action frames, iii) and is either a public action frame or amanagement frame, and the energy of the communication frame is lowerthan the first energy level threshold, resuming counting down the timerin the backoff procedure; and when the communication frame correspondsto an OBSS and is not a public action frame and is not a managementframe, and the energy of the communication frame is lower than a secondenergy level threshold, resuming counting down the timer in the backoffprocedure, wherein the second energy level threshold is higher than thefirst energy level threshold.
 9. The method of claim 8, furthercomprising: transmitting over the shared communication medium inresponse to the timer reaching a predetermined value.
 10. The method ofclaim 8, wherein: the communication frame complies with the first WLANcommunication protocol; and wherein identifying the BSS to which thecommunication frame corresponds comprises utilizing a BSS identifierincluded in a physical layer (PHY) preamble of the communication frame.11. The method of claim 8, wherein: the communication frame complieswith a second WLAN communication protocol that is a legacy protocol; andwherein identifying the BSS to which the communication frame correspondscomprises utilizing a MAC address included in a MAC layer header in thecommunication frame.
 12. The method of claim 8, wherein resumingcounting down the timer includes: decrementing the counter to accountfor idle time slots corresponding to Point Coordination Function (PCF)Interframe Space (PIFS) after one of the ending of HE PPDU header,ending of the first correctly decoded MPDU in an A-MPDU, or the endingof the MPDU.
 13. The method of claim 8, wherein resuming counting downthe timer includes: decrementing the counter to account for idle timeslots from a beginning of non-legacy portion of a physical layer (PHY)preamble of the communication frame.
 14. An apparatus, comprising: acommunication device having one or more integrated circuits configuredto communicate according to a first wireless local area network (WLAN)communication protocol, wirelessly receive a communication frame,measure an energy level of the communication frame, when the measuredenergy level of the communication frame meets a static clear channelassessment (CCA) criterion, identifying a basic service set (BSS) towhich the communication frame corresponds, wherein identifying the BSSto which the communication frame corresponds comprises i) utilizing aBSS identifier included in a physical layer (PHY) preamble of the framewhen the frame complies with the first WLAN communication protocol, orii) utilizing a media access control (MAC) address included in a MAClayer header of the communication frame when the communication framecomplies with a second WLAN communication protocol that is a legacyprotocol, when the communication frame corresponds to a same BSS withwhich the communication device is associated, processing thecommunication frame utilizing a first energy level threshold, when thecommunication frame i) corresponds to an overlapping BSS (OBSS), ii)includes a broadcast BSS identifier or a BSS identifier reserved forpublic action frames, and iii) is either a public action frame or amanagement frame, further processing the frame utilizing the firstenergy level threshold; and when the communication frame corresponds toan OBSS and is not a public action frame and is not a management frame,processing the communication frame utilizing a second energy levelthreshold that is higher than the first energy level threshold.
 15. Theapparatus claim 14, wherein: the communication frame is a data frame;the MAC address is one of a plurality of MAC addresses contained in theMAC layer header of the data frame; and the one or more integratedcircuit devices are further configured to utilize a distribution system(DS) value in the MAC layer header of the data frame to determine whichof the plurality of MAC addresses is the MAC address of an access point(AP) corresponding to the data frame.
 16. The apparatus of claim 15,wherein the one or more integrated circuits are further configured todetermine that the data frame corresponds to the same BSS with which thecommunication device is associated when the MAC address of the AP in theMAC layer header is the same as a MAC address of an AP with which thedevice is associated.
 17. The apparatus of claim 15, wherein: the frameis a control frame; and the one or more integrated circuits are furtherconfigured to determine whether the control frame corresponds to thesame BSS with which the device is associated based on whether thecontrol frame is used to acknowledge a data unit in the BSS with whichthe device is associated.